MTJ Stack Lattice-Matching Layer for High-Temperature Stability
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Solution Overview
Problem
Magnetic tunnel junction (MTJ) stacks used in spin transfer torque magnetic random access memories (STT-MRAMs) face challenges with synthetic anti-ferrimagnetic coupling loss at high temperatures and dipole field interference, which affects their performance and stability.
Innovation Solution
The design of MTJ stacks incorporates a first and second pinning layer with lattice-matching layers of platinum or palladium, a synthetic anti-ferrimagnetic coupling layer, and a structure blocking layer, which maintains magnetic alignment and reduces dipole field effects through improved lattice matching and layer structure optimization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional MTJ stacks are processed at high temperatures (≥400°C), then manufacturing completeness is achieved, but synthetic anti-ferrimagnetic coupling is lost and dipole field interference increases
Solution Approach 1:
A lattice-matching layer comprising platinum or palladium is introduced between the pinning layer and the synthetic anti-ferrimagnetic coupling layer. This intermediary layer serves as a buffer that maintains lattice matching during high-temperature processing, preventing coupling loss while allowing the necessary thermal processing to occur.
Solution Approach 2:
The patent employs a composite structure combining the pinning layer, lattice-matching layer (platinum or palladium), and synthetic anti-ferrimagnetic coupling layer. This composite material system is specifically designed to maintain magnetic coupling stability through high-temperature processing by leveraging the lattice-matching properties of the platinum or palladium layer.
2Ease of manufacture
If conventional MTJ stacks are processed at high temperatures (≥400°C), then manufacturing completeness is achieved, but dipole field interference increases
Solution Approach 1:
The lattice-matching layer acts as a mediator that allows high-temperature processing to proceed while preventing the generation of harmful dipole fields. By maintaining proper lattice matching, it ensures that the magnetic layers are properly aligned and coupled, reducing dipole field interference despite the high processing temperatures.
Solution Approach 2:
The patent changes the structural parameters of the MTJ stack by inserting the lattice-matching layer, which alters the thermal and magnetic properties of the overall structure. This parameter change enables the system to withstand high-temperature processing without generating excessive dipole field interference.
3Reliability
If lattice-matching layers of platinum or palladium are added, then magnetic coupling stability is maintained, but device complexity increases
Solution Approach 1:
The lattice-matching layer is applied locally at specific interfaces (between the pinning layer and coupling layer) where it is most needed to maintain stability during high-temperature processing. This localized application minimizes the overall added complexity while providing the necessary stability enhancement.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration enhances the stability and performance of MTJ stacks by maintaining magnetic and electrical properties even after high-temperature processing, reducing dipole field interference, and ensuring consistent operation.
Implementation Method 1
a first pinning layer comprising a first bilayer and a first lattice-matching layer formed over the first bilayer, wherein the first lattice-matching layer includes platinum or palladium
Implementation Method 2
a synthetic anti-ferrimagnetic coupling (SyF) layer in between the first pinning layer and the second pinning layer. The SyF coupling layer causes surface atoms of the first pinning layer and the second pinning layer, when exposed to a magnetic field, to align with surface atoms of the SyF coupling layer, thereby pinning the orientation of the magnetic moments
Implementation Method 3
Spin transfer torque magnetic random access memories, or STT-MRAMs, employ magnetic tunnel junction structures in the memory cells thereof
Data Source
AI summary
Embodiments of magnetic tunnel junction (MTJ) structures discussed herein employ a first pinning layer and a second pinning layer with a synthetic anti-ferrimagnetic layer disposed therebetween. The first pinning layer in contact with the seed layer can contain a single layer of platinum or palladium, alone or in combination with one or more bilayers of cobalt and platinum (Pt), nickel (Ni), or palladium (Pd), or combinations or alloys thereof, The first pinning layer and the second pinning layer can have a different composition or configuration such that the first pinning layer has a higher magnetic material content than the second pinning layer and/or is thicker than the second pinning layer. The MTJ stacks discussed herein maintain desirable magnetic properties subsequent to high temperature annealing.